Question

我编写了一个代码来获取所有用户的电子邮件，然后将其保存在txt文件中，但有些用户没有电子邮件，因为他们使用电话号码注册所以当我试图去取它转储在txt文件中 http://prntscr.com/5wf7cv

我希望如果单元格为空/ NULL则不提取任何内容任何人都可以帮我修复它吗？

    $sql=mysql_query("SELECT * FROM user  "); 
    while($row = mysql_fetch_array($sql)) {

 $email = $row['email']   ;

  $fp = fopen("emaillist.txt", "a");
$savestring = "\n$email";
fwrite($fp, $savestring);
fclose($fp);
}
echo  "DONE ";

Answer 1

将查询更改为

SELECT * FROM user  WHERE email != NULL

Answer 2

试试这个：

$sql=mysql_query("SELECT * FROM user  "); 
while($row = mysql_fetch_array($sql)) {


    if (strlen($row['email'] ) > 0){
        $email = $row['email'];
        $fp = fopen("emaillist.txt", "a");
        $savestring = "\n$email";
        fwrite($fp, $savestring);
        fclose($fp);
    }
}
echo  "DONE ";

Answer 3

SELECT * FROM user  WHERE email IS NOT NULL

检查NULL值的唯一方法是

column IS NULL或column IS NOT NULL

如果单元格为空，则不会从数据库中获取电子邮件

3 个答案: